The _CodexCompletionsAdapter (used for compression, vision, web_extract,
session_search, and memory flush when on the codex provider) streamed
responses but discarded all events with 'for _event in stream: pass'.
When get_final_response() returned empty output (the same chatgpt.com
backend-api shape change), auxiliary calls silently returned None content.
Now collects response.output_item.done and text deltas during streaming
and backfills empty output — same pattern as _run_codex_stream().
Tested live against chatgpt.com/backend-api/codex with OAuth.